Add deck synergy suggestions, a responsive deck layout, and undoable library bulk-add

Suggestion scoring is fully offline (tribal/mechanic/archetype/mana-base
signals derived at ingest, no external synergy database), with an "unusual
picks" mode that surfaces underappreciated cards instead of staples. The
deck page's top panels now use a CSS grid so wide windows don't waste
horizontal space. Library's bulk add-to-deck can clobber existing deck
quantities, so it now offers an undo (snackbar + command palette, the
latter with no timeout) that restores each card's prior state exactly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/views/LibraryBrowser.tsx

@@ -26,8 +26,19 @@ const REMOVAL_GRACE_MS = 5000;
 
 const NO_FACETS: LibraryFacets = { types: [], subtypes: [], keywords: [] };
 
-/** Browse & filter the owned library by name and card criteria. */
-export function LibraryBrowser() {
+/**
+ * Browse & filter the owned library by name and card criteria.
+ *
+ * `onOfferUndo` is threaded in from `App` (rather than owning an `UndoBar`
+ * here) so the resulting "Undo" is also reachable from the command palette,
+ * which is mounted at the app level and outlives this view across tab
+ * switches.
+ */
+export function LibraryBrowser({
+  onOfferUndo,
+}: {
+  onOfferUndo: (message: string, run: () => void | Promise<void>) => void;
+}) {
   const [text, setText] = useState("");
   const [commander, setCommander] = useState(0);
   const [colorsInclude, setColorsInclude] = useState(0);
@@ -178,6 +189,12 @@ export function LibraryBrowser() {
    * cards already in the deck rather than skipping them, so it doubles as a
    * bulk "fix the land count" tool. `bulkToMaybeboard` sends them to the
    * deck's maybeboard instead of the mainboard.
+   *
+   * Since this overwrites rather than skips, it can clobber an existing
+   * in-deck quantity/board — so it snapshots each target's prior deck_cards
+   * row (or absence of one) first and offers an "Undo" that restores exactly
+   * that prior state (deleting the row again for cards that weren't in the
+   * deck before).
    */
   async function bulkAddToDeck(mode: "one" | "all") {
     if (bulkDeckId === "") return;
@@ -186,6 +203,8 @@ export function LibraryBrowser() {
     setBulkBusy(true);
     try {
       const targets = rows.filter((r) => selected.has(r.oracle_id));
+      const before = await api.deckContents(deck.id);
+      const prevByOracle = new Map(before.map((e) => [e.oracle_id, e]));
       await Promise.all(
         targets.map((r) =>
           api.setDeckCard(
@@ -198,6 +217,24 @@ export function LibraryBrowser() {
         ),
       );
       setRefreshKey((k) => k + 1);
+      onOfferUndo(
+        `Added ${targets.length} card${targets.length === 1 ? "" : "s"} to ${deck.name}.`,
+        async () => {
+          await Promise.all(
+            targets.map((r) => {
+              const prev = prevByOracle.get(r.oracle_id);
+              return api.setDeckCard(
+                deck.id,
+                r.oracle_id,
+                prev?.quantity ?? 0,
+                prev?.is_commander ?? false,
+                prev?.is_maybeboard ?? false,
+              );
+            }),
+          );
+          setRefreshKey((k) => k + 1);
+        },
+      );
     } finally {
       setBulkBusy(false);
     }